Alfred Wegener’s Continental Drift Hypothesis

One hundred years ago today Alfred Wegener presented his Continental Drift hypothesis to much derision and scepticism. -Deskarati -

Alfred Wegener first thought of this idea by noticing that the different large landmasses of the Earth almost fit together like a jigsaw. The Continental shelf of the Americas fit closely to Africa and Europe, and Antarctica, Australia, India and Madagascar fit next to the tip of Southern Africa. But Wegener only took action after reading a paper in Autumn 1911 and seeing that a flooded land-bridge contradicts isostasy. Wegener’s main interest was meteorology, and he wanted to join the Denmark-Greenland expedition scheduled for mid 1912. So he hurried up to present his Continental Drift hypothesis on January 6, 1912. He analyzed either side of the Atlantic Ocean for rock type, geological structures and fossils. He noticed that there was a significant similarity between matching sides of the continents, especially in fossil plants. His hypothesis was thus strongly supported by the physical evidence, and was a pioneering attempt at a rational explanation.

Fossil patterns across continents (Gondwanaland).

From 1912, Wegener publicly advocated the theory of “continental drift”, arguing that all the continents were once joined together in a single landmass and have drifted apart. He supposed the cause might be the centrifugal force of the Earth’s rotation (“Polflucht”) or the astronomical precession. Wegener also speculated on sea-floor spreading and the role of the mid-ocean ridges, stating: the Mid-Atlantic Ridge … zone in which the floor of the Atlantic, as it keeps spreading, is continuously tearing open and making space for fresh, relatively fluid and hot sima [rising] from depth. However, he did not pursue these ideas in his later works.

In 1915, in The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), Wegener published the theory that there had once been a giant continent, he named “Urkontinent” (German word meaning “origin of the continents”, in a way equivalent to the Greek “Pangaea”, meaning “All-Lands” or “All-Earth”) and drew together evidence from various fields. Expanded editions during the 1920s presented the accumulating evidence. The last edition, just before his untimely death, revealed the significant observation that shallower oceans were geologically younger.

Reaction

In his work, Wegener presented a large amount of very strong evidence in support of continental drift, but the mechanism remained elusive. While his ideas attracted a few early supporters such as Alexander Du Toit from South Africa and Arthur Holmes in England, the hypothesis was generally met with skepticism from largely conservative scientists, who were resistant to any change in the status quo. The one American edition of Wegener’s work, published in 1925, was received so poorly that the American Association of Petroleum Geologists organized a symposium specifically in opposition to the continental drift hypothesis. Its opponents could argue, as did the Leipziger geologist Franz Kossmat, that the oceanic crust was too “firm” for the continents to “simply plough through”, a suggestion which ignored the plasticity of all rocks at depth and at high temperatures and pressures. The comment also ignored the vast time-scale over which continental drift has occurred, effectively the total age of the earth of about 4.5 billion years.

In 1943 George Gaylord Simpson wrote a vehement attack on the theory (as well as the rival theory of sunken land bridges) and put forward his own permanentist views. Alexander du Toit wrote a rejoinder in the following year, but G.G.Simpson’s influence was so powerful that even in countries previously sympathetic towards continental drift, like Australia, Wegener’s hypothesis fell out of favour.

One Response to Alfred Wegener’s Continental Drift Hypothesis

It was interesting to read over some of the history of the Wegener theory. What it doesn’t mention is that it had something of a renaissance in the late fifties with the inevitable accumulation of more evidence, notably the “samfrau geosyncline”, the Permian(?) glaciation, and Mososaur distribution. All of these are pieces of “killer evidence”, because if you don’t accept continental drift you are very hard-pressed to explain them in any other way. This was enough to convince me at the time, as a biology undergraduate.

In 1967, when I became a college lecturer, I tested my new geography colleagues by asking them what they thought of Wegener’s theory. Both poo-pooed it without really knowing much about the modern evidence. Within two years they were teaching it as the new orthodoxy. Tis was, to me, an excellent illustration of Kuhn’s “paradigm shift”.

If you want to know more about the “samfrau geosyncline”, the Permian(?) glaciation, and Mososaur distribution I shall attempt to find the original article which I am sure I still have.